The US and Israel will commence the largest-ever joint air defense drill of its kind in Israel on October 21, an army source said on Tuesday.

The exercise, named Austere Challenge 12, was originally scheduled for last spring but was postponed due to regional tensions with Iran.

On October 14, large numbers of American soldiers are expected to begin arriving in Israel, where they will set up aerial defense positions on Israeli territory and on US Navy vessels off the Israeli coastline.

The three-week drill will simulate various missile defense scenarios, and is expected to end with a live-fire interception of a decoy incoming Patriot missile.